Full Idea
Void makes it impossible for anything to move, since in a void there is nowhere for a thing to move to more or less than anywhere else, because the void by definition contains no differentiation.
Clarification
'Void' is total emptiness
Gist of Idea
Movement is impossible in a void, because nothing can decide the direction of movement
Source
comment on Democritus (fragments/reports [c.431 BCE]) by Aristotle - Physics 214b32
Book Reference
Aristotle: 'Physics', ed/tr. Waterfield,Robin [OUP 1996], p.95
A Reaction
A lovely application of the Principle of Sufficient Reason. However this assumes that the cause of the movement is going to be in the void (telos?), rather than in the body which will move (modern causation?).